1. Field of the Invention
The present invention relates to a dynamoelectric machine such as an automotive alternator, etc., and particularly relates to a permanent magnet fixing construction in a Lundell rotor.
2. Description of the Related Art
Automotive alternators that use Lundell rotors have been used in automobiles for decades. Loads from electrical equipment that is mounted due to environmental issues have been increasing rapidly in recent years, and further increases in generated power are being sought from Lundell rotors.
If attempts are made to answer these demands within the scope of conventional design, the alternators are invariably increased in size. Increases in alternator size increase weight and installation space.
Conventionally, in order to solve such problems, a rotor assembly has been proposed in which permanent magnets are held by a strap on mounting surfaces that are disposed on a yoke portion (see Patent Literature 1, for example).
Patent Literature 1: Japanese Patent Laid-Open No. 2004-153994 (Gazette)
In conventional rotor assemblies, because the permanent magnets are held on the mounting surfaces of the yoke portion by a fastening force from the strap, centrifugal forces act in a direction that loosens the fastening force of the strap on the permanent magnets during rotation of the rotor. Thus, one problem has been that the fastening force on the permanent magnets from the strap becomes loose, allowing the permanent magnets to wobble due to vibrations from the engine, etc., and generate noise.
Now, it is conceivable that the wobbling of the permanent magnets could be suppressed by fixing the permanent magnets to the strap and the mounting surfaces of the yoke portion using an adhesive. However, the adhesive cannot be injected between the strap and the permanent magnets and between the permanent magnets and the mounting surfaces when the permanent magnets are held on the mounting surfaces by the strap. Thus, the adhesive would have to be applied to the permanent magnets and the strap before the permanent magnets are held on the mounting surfaces, making handling of the magnetized permanent magnets and the strap problematic and reducing mass producibility.